The present invention is concerned with test strips and with a process for the production thereof.
More particularly, the present invention is concerned with a process for the production of an analysis strip with a longitudinal carrier upon which is fixed at least one test field, in which the test field material is produced batchwise in an amount sufficient for a plurality of test strips and thereafter, in a chronologically separated working step, is continuously fixed in the form of a band onto a parallel-running, substantially wider band of test strip band finally being divided transversely to its longitudinal direction into a plurality of test strips. Furthermore, the present invention is directed to a test strip for the analysis of components of a liquid, especially of a human body fluid, with a longitudinal carrier with a front end and a rear end, close to the front end there being applied at least one test field for an analysis and close to the rear end a holding region is provided in order to facilitate moistening the test strip with a liquid and carrying out of the evaluation, the test strip also being provided with a mechanically readable coding in the form of lines running substantially transversely to the test strip.
In recent years, analytical determinations, especially for medical purposes, have been carried out to an increasing extent with the help of test strips. The handling of these test strips is very simple. Urine test strips are generally briefly dipped into a sample and the liquid subsequently simply allowed to drip off. For blood investigations, a drop of blood is usually applied and again wiped off after it has fully soaked into the test field. However, other methods are also possible. In the case of the conventional test strips, on the test fields there takes place a chemical reaction between component materials of the body fluid and reagents present on the test field, which leads to a color change of the test field. In the initial period of analysis with test strips, the color change was evaluated visually.
The visual evaluation of the color change only permits a qualitative or semi-quantitative assessment of the concentration of the material to be analyzed. However, because of the simple handling and the favorable costs of the test strips for smaller series of investigations, already for quite a long time an endeavour has been made to quantitatively evaluate the color change with the help of appropriate apparatus. Usually, use is made of a reflection photometer which determines the degree of reflection of the test field surface, after the reaction has taken place, at one or more wavelengths.
A difficult problem in the case of these endeavours is caused by the fact that the test fields of the test strips, which usually consist of papers or fleeces impregnated with appropriate reagents and dried, cannot be so well reproducibly produced that they can then also be evaluated with the desired degree of exactitude if they originate from different production batches. Because of this, various suggestions have already been made to provide the evaluation device with typical, i.e. batch-specific, information for a particular production batch, especially the particular dependence of the concentration of the substance to be analyzed upon the particular degree of reflection. For example, for this purpose, interchangeable scales are employed which, in each case, are contained in the test strip packings and can be introduced into the appropriate apparatus in order to calibrate it for a particular batch. The necessary evaluation information can also be provided in mechanically readable form, for example as punched or magnetic cards in the packing. However, these methods suffer from considerable disadvantages. In particular, there is a great danger of confusion because the variable scales or punched cards must be changed by hand every time a new test strip packing is opened. If this is not done, then it results unavoidably in erroneous measurements which, especially in the field of medicine, can have serious results.